Polymeric materials are generally characterized by electric insulation, flexibility and light weight. They are used in electric and electronic applications, for example, as dielectrics in film capacitors, field effect transistors, resin antennas, and the like. Also transparent resins allowing for light transmission are useful materials finding widespread use in optical devices such as lenses and waveguides and imaging devices such as displays.
The film capacitors are required to have a greater capacitance and a smaller size. It is known that the capacitance of a film capacitor is in proportion to the dielectric constant of a film and in inverse proportion to the thickness thereof. Therefore, among films of an identical thickness, a film having a higher dielectric constant is preferable, because the capacitance of a capacitor is increased, that is, a film capacitor of higher capacitance is obtainable. Although polymeric materials such as polypropylene, polyester and polyphenylene sulfide are often used in the film capacitors, they have a low dielectric constant when used alone. One solution is disclosed in Patent Document 1 as a polymer composition comprising polyphenylene sulfide and a dielectric ceramic such as strontium titanate, which is used in capacitors and antennas.
With respect to the material for use in resin antennas, Patent Document 2 discloses a dielectric elastomer laminate including an intermediate layer of an elastomer having a dielectric ceramic added thereto to increase its dielectric constant. It contributes to the manufacture of antennas of higher frequency and smaller size. As to synthetic resins for use as the insulating film in FETs, a resin with a higher dielectric constant is preferable because the transistor capacitance is increased.
An actuator adapted to convert an input of certain energy to an output of mechanical energy is one of transducers. The actuator is divided into several types. Since an actuator using a dielectric elastomer or polymeric material is capable of converting electrical energy to mechanical energy and takes the form of a flexible thin film, its application to a variety of equipment such as micro-pumps and speakers is under study (see Patent Document 3). Inversely, it is also known to use a dielectric elastomer in a transducer capable of converting mechanical energy to electrical energy (see Patent Document 4). An amount of deflection induced upon application of a voltage to a dielectric elastomer sandwiched between electrodes is in proportion to the dielectric constant of the elastomer. For the purpose of achieving a higher energy conversion efficiency, it is desirable to increase the dielectric constant. For example, Patent Document 5 discloses a dielectric elastomer which is obtained by dispersing dielectric ceramic particles having a dielectric constant of at least 1,000 in crosslinked rubber.
In these applications, resins having a high dielectric constant are needed. The dielectric constant of a polymeric material may be increased by blending a dielectric ceramic such as strontium titanate therein. To gain a satisfactory effect, the ceramic must be blended in a large amount, which undesirably causes the material to become hard and difficult to mold. In order that an inorganic material such as dielectric ceramic be mixed and dispersed uniformly in a polymeric material, a special treatment, for example, surface treatment with silane coupling agents is necessary. Further, the dielectric ceramic has a high specific gravity, which can detract from the lightweight feature characteristic of polymeric material.
Patent Document 6 describes the use of fluoro-polymers having a high dielectric constant such as vinylidene fluoride. However, the fluoro-polymers are expensive and less versatile.